df.streamspraydf: allow callable, time-dependent progenitor_mass

[jobovy]

Summary

• progenitor_mass on basestreamspraydf / chen24spraydf / fardal15spraydf now accepts either a scalar/Quantity (existing behaviour) or a callable M(t) of the progenitor-time coordinate (t=0 is now, t<0 is past).
• Quantity input and/or output of the callable are auto-detected with the four-branch pattern from AnyAxisymmetricRazorThinDiskPotential.
• Internally the value is stored as self._progenitor_mass_fn and evaluated at each particle's stripping time in _calc_rtide and in the Chen24 escape-velocity calculation. The legacy self._progenitor_mass attribute is kept, pinned to the present-day mass.
• New tests in tests/test_streamspraydf.py (callable=scalar equivalence, evolving-mass tidal-radius scaling, attribute back-compat, vectorisation) and in tests/test_quantity.py (all three Quantity in/out combinations, both spray models).
• Tutorial notebook gains a worked example contrasting constant-mass and growing-mass progenitors.

Test plan

• pytest tests/test_streamspraydf.py — 27 passed
• pytest tests/test_quantity.py -k 'streamspraydf or progmass' — 7 passed (3 new + 4 existing)
• jupyter nbconvert --to notebook --execute --inplace doc/source/tutorials/streams/streamspraydf.ipynb — executes cleanly
• pre-commit hooks pass

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.92%. Comparing base (9d0d8c5) to head (37c5b2e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #880   +/-   ##
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  Coverage   99.92%   99.92%           
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  Files         225      225           
  Lines       33875    33911   +36     
  Branches      710      710           
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+ Hits        33848    33884   +36     
  Misses         27       27           

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